The invention relates to a device for retaining doctor blades with a bottom plate and a top plate, wherein the bottom plate and the top plate are hingedly connected to each other via a pivot bearing and the doctor blade is affixed to the top plate, wherein an expandable tube is provided between the bottom plate and the top plate on each side of the pivot bearing.
A scraping device or doctor blade has the task, among others, to clean the surface of a roller or a cylinder. In the case of a paper machine, such a doctor blade has the effect that the paper web guided across the respective roller of the paper machine is not wound up on the roller in the event of a web break, but exits the roller at the predetermined position to reach, for example, a collection tray. This doctor blade must ensure that this task is performed with 100% certainty, since otherwise considerable failures would occur in the papermaking process, possibly even damage the paper machine. The doctor blade also has the task to clean the surface of the roller so that the paper web is not marked. For this reason, the doctor blade attached to its retaining device must be in contact with the roller as uniformly as possible over its entire length. For pressing the doctor blade onto the roller surface, the retaining device is generally constructed in two parts and has a bottom plate which is typically attached on the machine frame. A top plate is pivotally attached on this bottom plate, so that the doctor blade can be lifted off the roller surface, or placed on and pressed against the roller surface (EP 1567715 B1).
It has been shown that, especially in the wet parts of the paper machine relatively strongly contaminate the retaining devices, requiring frequent cleaning. For this purpose, the top plate must be removed from the bottom plate so that the retaining device can be opened. WO 2004/042 143 A1 discloses a doctor blade retaining device wherein the bottom plate has a bearing tube and the top plate is pivotally mounted around the bearing tube. To open this retaining device, the top plate is withdrawn in the axial direction from the bearing tube, thereby allowing access to the interior space. With rollers that can have a length of 12 m the retaining device for the doctor blade must also have this length, and it has been found that with such a length, the frictional forces along the bearing tube are relatively large, so that the top plate can be withdrawn or pushed on only with difficulty.
WO 2009/076 128 A1 also discloses a retaining device for doctor blades. However, this retaining device is complicated to manufacture since it is made of a continuous casting part, which has to be machined even further. This retaining device also tends to be heavily contaminated. AT 503 922 A4 also shows such retaining device.